Question: Which of these numbers is composite? ${2,\ 17,\ 31,\ 41,\ 65}$
Answer: A composite number is a number that has more than two factors (including 1 and itself). 2, 17, 31, and 41 each have only two factors. The factors of 65 are 1, 5, 13, and 65. Thus, 65 is the composite number.